1. Field of the Application
The subject application relates to a bladed drum of an axial compressor. More particularly, the subject application relates to a drum on which the rotor blades are attached through positive material contact. The subject application also relates to a turbomachine fitted with such a drum.
2. Description of Related Art
An axial turbomachine compressor preferably has several compression stages. Each compression stage comprises an annular row of rotor blades and an annular row of stator blades. A compressor rotor may be formed of a drum with an axially symmetric wall, which creates a lightweight and economical one-piece element.
A drum has a generally annular thin wall to which the rotor blades are attached directly. Several solutions for achieving that are possible. The blades can be welded into apertures in the drum wall or the blade roots can be inserted into axial grooves cut into the drum.
Alternatively, the drum can be provided with annular recesses in which there are mounting surfaces. The rotor blades have corresponding mounting surfaces enabling them to be clamped into the recesses.
Patent EP 2075417 A1 discloses a rotor drum of an axial turbomachine compressor. The drum has a symmetrical wall and annular recesses. The latter open radially outwards and have constrictions in the same direction. The blades are clamped within the annular recesses. For this purpose they have feet whose profiles correspond to the recesses and are inserted into them. They are thus retained radially. The existence of the recesses requires a large mass of material, which makes the drum heavier. Also, this material represents a cost. In addition, an annular recess forms a material discontinuity in the drum wall as it extends radially to the drum wall. It reduces its stiffness, resulting in increased flexing when the turbomachine is operating. The blade roots are pulled outwards due to the centrifugal force. Because of their shape, they tend to separate from the inner edges of the annular recesses, which further distorts the drum. Each annular recess has clamping surfaces which have to be machined. Because of the closed nature of the recesses, the clamping surfaces are relatively inaccessible, making machining complicated.
Although great strides have been made in the area of bladed drums for axial compressors, many shortcomings remain.